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Heliophysics (from the prefix "helio", fromAttic Greekhḗlios, meaning Sun, and the noun "physics": the science of matter and energy and their interactions) is the physics of the Sun and its connection with theSolar System.[1]NASA defines[2] heliophysics as "(1) the comprehensive new term for the science of the Sun - Solar System Connection, (2) the exploration, discovery, and understanding of Earth's space environment, and (3) the system science that unites all of the linked phenomena in the region of the cosmos influenced by a star likeour Sun."
Heliophysics is broader thanSolar physics, that studies the Sun itself, including its interior, atmosphere, and magnetic fields. It concentrates on the Sun's effects onEarth and other bodies within the Solar System, as well as the changing conditions in space. It is primarily concerned with themagnetosphere,ionosphere,thermosphere,mesosphere, andupper atmosphere of the Earth and otherplanets. Heliophysics combines the science of the Sun,corona,heliosphere andgeospace, and encompasses a wide variety of astronomical phenomena, including "cosmic rays andparticle acceleration,space weather andradiation,dust andmagnetic reconnection, nuclear energy generation and internal solar dynamics,solar activity andstellar magnetic fields,aeronomy andspace plasmas,magnetic fields andglobal change", and the interactions of the Solar System with theMilky Way Galaxy.
Term "heliophysics" (Russian:гелиофизика) was widely used inRussian-languagescientific literature. TheGreat Soviet Encyclopedia third edition (1969–1978) defines "Heliophysics" as "[...] a division ofastrophysics that studiesphysics of the Sun".[3] In 1990, theHigher Attestation Commission, responsible for the advancedacademic degrees inSoviet Union and later inRussia and theFormer Soviet Union, established a new specialty "Heliophysics and physics of solar system". InEnglish-language scientific literature prior to about 2001, the term heliophysics was sporadically used to describe the study of the "physics of the Sun".[4] As such it was a direct translation from the French "héliophysique" and the Russian "гелиофизика". In 2001, Joseph M. Davila, Nat Gopalswamy andBarbara J. Thompson at NASA'sGoddard Space Flight Center adopted the term in their preparations of what became known as theInternational Heliophysical Year (2007–2008), following 50 years after theInternational Geophysical Year; in adopting the term for this purpose, they expanded its meaning to encompass the entire domain of influence of the Sun (theheliosphere). As an early advocate of the newly expanded meaning,George Siscoe offered the following characterization:
"Heliophysics [encompasses] environmental science, a unique hybrid betweenmeteorology andastrophysics, comprising a body of data and a set of paradigms (general laws—perhaps mostly still undiscovered) specific to magnetized plasmas and neutrals in the heliosphere interacting with themselves and with gravitating bodies and their atmospheres."
Around mid-2006,Richard R. Fisher, then Director of the Sun-Earth Connections Division of NASA'sScience Mission Directorate, was challenged by the NASA administrator to come up with a concise new name for his division that "had better end on 'physics'".[5] He proposed "Heliophysics Science Division", which has been in use since then. The Heliophysics Science Division uses the term "heliophysics" to denote the study of the heliosphere and the objects that interact with it – most notably planetary atmospheres and magnetospheres, the solar corona, and theinterstellar medium.
Heliophysical research connects directly to a broader web of physical processes that naturally expand its reach beyond NASA's narrower view that limits it to the Solar System: heliophysics reaches fromsolar physics out tostellar physics in general, and involves several branches ofnuclear physics,plasma physics,space physics andmagnetospheric physics. The science of heliophysics lies at the foundation of the study ofspace weather, and is also directly involved in understandingplanetary habitability.
The Sun is an activestar, and Earth is located within itsatmosphere, so there is a dynamic interaction. The Sun' light influences all life and processes on Earth; it is an energy provider that allows and sustainslife on Earth. However, the Sun also produces streams ofhigh energy particles known as thesolar wind, and radiation that can harm life or alter its evolution. Under the protective shield ofEarth's magnetic field and its atmosphere, Earth can be seen as an island in the universe where life has developed and flourished.[6][7]
The intertwined response of the Earth andheliosphere are studied because the planet is immersed in this unseen environment. Above the protective cocoon of Earth's lower atmosphere is a plasma soup composed of electrified and magnetized matter entwined with penetrating radiation and energetic particles. Modern technologies are susceptible to the extremes ofspace weather — severe disturbances of the upper atmosphere and of the near-Earth space environment that are driven by the magnetic activity of the Sun. Strong electrical currents driven in the Earth's surface during auroral events can disrupt and damage modern electric power grids and may contribute to the corrosion of oil and gas pipelines.[8]
Methods have been developed to see into the internal workings of the Sun and understand how theEarth's magnetosphere responds tosolar activity. Further studies are concerned with exploring the full system of complex interactions that characterize the relationship of the Sun with theSolar System.[6][7]
There are three primary objectives that define the multi-decadal studies:[6][9]
Plasmas and their embedded magnetic fields affect the formation and evolution of planets and planetary systems. The heliosphere shields the Solar System from galactic cosmic radiation. Earth is shielded by itsmagnetic field, protecting it from solar and cosmic particle radiation and from erosion of the atmosphere by thesolar wind. Planets without a shielding magnetic field, such asMars andVenus, are exposed to those processes and evolve differently. OnEarth, the magnetic field changes strength and configuration during its occasional polarity reversals, altering the shielding of the planet from external radiation sources.[10]
Determine changes in theEarth's magnetosphere, ionosphere, and upper atmosphere in order to enable specification, prediction, and mitigation of their effects. Heliophysics seeks to develop an understanding of the response of the near-Earth plasma regions tospace weather. This complex, highly coupled system protects Earth from the worst solar disturbances while redistributing energy and mass throughout.[9][10]
This article incorporatespublic domain material fromHeliophysics.National Aeronautics and Space Administration. This article incorporatespublic domain material fromBig Questions.National Aeronautics and Space Administration. This article incorporatespublic domain material fromFocus Areas.National Aeronautics and Space Administration.| Internal structure | |||||||
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